Electroless plating is a widely adopted technology for functionalizing the surface of an insulative material such as: various kinds of plastic, glass, ceramic, and wood. In the electroless plating process, a reducing agent is put in an aqueous solution of metallic salt, so as to precipitate metal on a base material, without a use of electric energy, through a reduction process caused by decomposition of the reducing agent. This electroless plating process can be, for example, a decorative plating process or a functional plating. The decorative plating process is for making a part such as: a grille and marks or the like of an automobile; and knobs or the like of home electronic appliances, by conducting electroless plating on ABS resin or polypropylene resin. The functional plating is for plating through holes of a printed-wiring board, by conducting the electroless plating on ABS resin or polypropylene resin.
However, in many cases, the electroless plating results in low adhesiveness to the surface of the above mentioned various materials. This low adhesiveness of the electroless plating film to the insulative material has been a concern, particularly in the case of manufacturing a printed-wiring board. Especially, in a case of forming a metal layer on an insulative material having a smooth surface and a small surface roughness, it is extremely difficult to firmly adhere an electroless plating to the surface by the method of directly forming an electroless plating film.
This is believed to be caused mainly by a catalyst such as palladium which intervenes between the electroless plating and the surface. Accordingly, to improve the adhesiveness between the circuit wiring and the surface having a small surface roughness, a foundation layer of a metal needs to be formed on the surface of a polyimide film by a physical method such as vapor deposition or spattering, and a copper which is a favorable conductor is formed on the foundation layer thereafter (See Patent Citation 2).
Meanwhile, for example, to form an electroless plating film on an insulative material in manufacturing of a printed-wiring board or the like having thereon wiring, it is preferable that an electroless plating film be firmly formed on the smooth surface of the insulative material.
In order to solve the foregoing problem, the surface of an insulative resin material for printed-wiring board was roughened using various techniques, so that the adhesiveness between the electroless plating film and the surface is acquired by so-called Anchor Effect (See Patent Citation 1 for example). This however raises the following problem. Namely, since the adhesiveness between an electroless plating film and a resin material is low when the surface roughness of the material is small, the roughness of the material surface needs to be increased to achieve a good adhesiveness. This however causes limitation in formation of fine wiring.
[Patent Citation 1]
Japanese Unexamined Patent Publication No. 198907/2000 (Tokukai 2000-198907; published on Jul. 18, 2000)
[Patent Citation 2]
Japanese Unexamined Patent Publication No. 330728/1996 (Tokukaihei 8-330728; Published on Dec. 13, 1996)